The present invention relates to a vane cell pump comprising an electrical pump unit that has a pump chamber into and out of which a fluid can flow and also a rotor with a number of vanes that are arranged so that they can move in the rotor and by means of which the fluid can be compressed before flowing out from the pump chamber. The vane cell pump according to the invention also comprises a sound-damping mechanism into which the fluid can flow after flowing through the pump chamber and that has a sound-damping cover attached to a part of the pump chamber and defining a sound-damping volume, wherein a preliminary sound-damping mechanism with at least one preliminary sound-damping outlet from which the fluid can flow is arranged within the sound-damping volume.
Vane cell pumps of the type named above, which are also frequently called rotary vane pumps, are already known in various constructions from the prior art. Examples for vane cell pumps can be found in DE 100 24 699 A1, DE 199 36 644 B4, DE 102006 058 977 A1, DE 102006 058 978 A1, DE 102006 058 979 A1, and DE 10 2006 058 980 A1.
To be able to damp the noises generated when the vane cell pump is operating, the vane cell pumps known from the prior art use a sound-damping mechanism that can be formed, in particular, by a sound-damping cover mounted on a part of the vane cell pump (especially on a mounting plate) and defining, together with a part of the pump ring, a sound-damping volume. After passing through the pump ring within which the fluid is compressed, the fluid flows first into the sound-damping volume and then, after flowing through the sound-damping volume, the fluid leaves the vane cell pump through (at least) one fluid outlet opening that communicates in terms of carrying a flow with the sound-damping volume.
To further reduce the noise level while the vane cell pump is operating, it is further known from the prior art to use an additional preliminary sound-damping mechanism that can be arranged, in particular, within the sound-damping volume and has a preliminary sound-damping outlet from which the fluid can flow. The fluid compressed within the pump chamber flows first out from the pump chamber into the preliminary sound-damping mechanism, through this mechanism, out through the preliminary sound-damping outlet, and then into the remaining sound-damping volume. Then the fluid leaves the vane cell pump through (at least) one fluid outlet opening that communicates in terms of carrying a flow with the sound-damping volume.
The preliminary sound-damping mechanisms known from the prior art have slot-shaped preliminary sound-damping outlets through which the fluid must pass when leaving the preliminary sound-damping mechanism. In terms of flow, there is a cross-sectional jump from a large flow cross section within the preliminary sound-damping mechanism to a considerably smaller flow cross section when flowing through the slot-shaped preliminary sound-damping outlet. It has been shown that such a construction of the preliminary sound-damping outlet has a negative effect on the output of the vane cell pump. The noise level of this vane cell pump is indeed lower than in vane cell pumps that do not have additional preliminary sound-damping mechanisms. The geometry of the preliminary sound-damping outlet with a cross-sectional jump from a large flow cross section to a small flow cross section caused by the slot-shaped construction of the preliminary sound-damping outlet leads to noticeable output throttling of the vane cell pump.